Posted
by
samzenpus
on Thursday October 11, 2012 @09:02PM
from the just-a-little-flare-up dept.

another random user writes "Scientists in the Arctic have launched an urgent investigation into how solar storms can disrupt sat-nav. Studies have revealed how space weather can cut the accuracy of GPS by tens of metres. Flares from the Sun interact with the upper atmosphere and can distort the signals from global positioning satellites. The project is under way at a remote observatory on a windswept mountainside in the Norwegian archipelago of Svalbard in the High Arctic. The site was chosen for its isolation from electronic pollution and for its position in relation to the Earth's magnetic field which flows from space down towards the far North."

"Tens of metres" is not exactly very precise, and it makes rather a large difference in precision if this is 20 metres or 99 metres: the first is annoying, the second might severely impair your ability to navigate, although I'd question that a bit. I mean, line of sight usually works, and in storms when it doesn't you really shouldn't be navigating close enough to the ground or a potential collision that even 100 metres off would be a dangerous problem, so am I missing something or is not that big an issue? Annoying, yes, and I can see the issue in S&R (gets a lot colder than the -20 mentioned in TFA that close to the poles, hell it gets colder than that here sometimes), but is there any highly important usage case where it would be an extremely detrimental problem?

I'm also a bit curious why they don't just use DGPS [wikipedia.org] anyways, since that exists and it seems like it would solve the problem quite nicely. Added bonus that it helps even when there isn't a solar storm, and it's even more accurate than regular GPS.

Some modern GPWS systems actually use digitalized maps of the area, determining possible collisions not only by radar but by "looking" around the map using the GPS coordinates. Pretty sure it'd cause problems there, causing false alerts and not warning other times...

I didn't think they'd want to complicate such a simple but effective safety system by adding maps which are out of date as soon, if not before, they are loaded. GPWS already utilises inputs from altitude RADAR, barometric altitude, flap and gear sensors, IAS, ILS beacons and outer markers (and a couple other things I can't remember off the top of my head).

Airplanes don't care if there is a new street or changes to the city layout, and hills/other geographical features don't tend to move around too much - so maps get outdated actually very slowly. The reason why they are doing the whole thing is late warnings. Approaching steeper hills at more significant speeds can mean that the radar only tells the pilots to pull up when it's too late. As for all the things you mentioned, only the RADAR matters as far as ground proximity goes...:)

I didn't think of that. Of course, you'd be right - GPS isn't a replacement for ILS, it's an augmentation if anything. ILS would still be the primary signal base for instrument landing, since it uses a terminal narrowband beacon which is a: static and b: situated at the end of the runway and pointing directly outward into the glide slope. GPS would be used in situations where vision is obscured, the surrounding terrain is less than ideal (big mountains in the way for instance, or open ocean either end and t

Very cool in the Alaska brush. If GPS went out it would be like tossing Alaska general aviation back 50 years when they crashed into mountains a lot. Now we only crash into mountains on rare occasions.

The company I worked for helped develop ADS-B and was heavily involved in the Capstone Program [wikipedia.org]. ADS-B essentially forms a network between all airplanes and ground stations equipped to send and receive the signal. An airplane periodically (like every few seconds) broadcasts its location and vector so anyone who can receive the signal can tell where the other plane is and where it's heading in relation to it. The GPS that's a part of it also had terrain maps and will warn you if you're headed for a mountain. I'm pretty proud of the work we did on ADS-B. It's improved the safety of flying small airplanes in Alaska immensely and it's coming to the lower 48 States gradually.

As someone who flies small planes in the Alaska brush on a regular basis, I thank you and everybody else involved. It allows everybody to fly safer and once everyone else is on board, it will keep the other nemesis of Alaska bush flying - mid air collisions - from happening.

The company that flies the plane that I part own (Harris Air) was one of the first small operators to use Capstone. They love it.

GPS approaches are getting better http://www.aopa.org/flightplanning/articles/2012/120209faa-marks-gps-approach-milestone.html [aopa.org] but still lack decent altitude information. GPS uses a stepped approach method ie: at position X,Y you need to be at Z altitude as read from the approach plate ( or indicated on the GPS device ) whereas with the more tradition ILS approach providing a glide slope, you fly a standard 3 degree slope and are guided by the signal until decision height is reached.

It's the difference between your car telling you to turn left "here" when it actually means the junction 45m up the road. Which admittedly could be an even bigger problem for the special kind of twit who already drives into walls "because the satnav told me to".

"Tens of metres" is not exactly very precise, and it makes rather a large difference in precision if this is 20 metres or 99 metres: the first is annoying, the second might severely impair your ability to navigate, although I'd question that a bit.

Now you know how the researchers feel. That's good journalism, right there, letting you experience the effects of a solar storm from your Slashdot armchair.

I'm a surveyor, and I use GPS to locate points to within a few hundredths of a foot (a couple centimeters, if you will). So, I don't know if my interpretation is exactly what the article intended, but I saw "tens of meters" and immediately thought "really really bad" and didn't even consider the possibility that the range of variation in "tens of meters" would be significant...

It's interesting how our minds immediately write things off like that... In most other circumstances I think I would have went exactly where you did and asked about the precision.

Something like... if you or I heard that it would cost "several billion dollars" to buy out a particular company, we'd just go "whoa, that's a lot"... but there's a select subset of people who would perk up their ears and say "umm, how much is 'several'?"

Because ionospheric corrections require 1) reasonably nearby ground stations measuring them, and 2) a data link between the ground stations and the receiver. In the high arctic, you seldom have either. WAAS is US only. Sweden does have a GPS augmentation system, though, one which uses ground-based transmitters to send out correction signals.

WAAS is specifically the US SBAS (satellite based augmentation system). There are others - europe, for example, has EGNOS, which is compatible with WAAS receivers. However, both systems broadcast from geostationary satellites, which are very low to the horizon at high latitudes so hard to receive.

I presume there is a good technical reason why they don't broadcast the SBAS signals directly from the NavStar satellites, but I don't know what it is (I would be very interested if someone who knows could explain

Differential GPS [wikipedia.org] can reduce that error of "tens of meters" to a few inches, even in a solar storm. A ground station at known location calculates the error and transmits it to the mobile GPS receiver, which adds the error into its location calculations.

In theory it can, but in practice, we can't calculate the correction fast enough during serious storms. The CPOS system normally provides real-time cm-precision positioning in Norway, but it breaks down during some storms. Improving this is a subject of research. See this article for details: http://www.swsc-journal.org/articles/swsc/pdf/2012/01/swsc120026.pdf

Because it'd be hideously expensive to get enough base stations to cover enough landmass to help sat-navs. If my company (which makes lorry fleet tracking equipment software) wanted to use DGPS, we'd have to get base stations installed throughout the UK, Switzerland, Germany, the US, and Australia.

I've been working on ionospheric impacts on GPS damn near since GPS was launched. Comments:

1. Ten meters is indeed not a hell of a lot until you consider things like (a) your average airport runway is likely not much more than 20 meters in width, particularly in areas where there probably isn't other forms of landing assistance and GPS is needed, and (b) while ten meters horizontally can be OK, ten meters vertically can be brutally bad if you're trying to land an airplane in bad weather and are depending

I don't get why this is "urgent". It's not a new issue. It's not unknown. It's not unexpected. Seems more like a perfectly normal investigation to gather data to help better understand and compensate for a known phenomenon.

Interestingly they control satellites from Svalbard, not the other way around:)

Kongsberg Satellite Services operates both SvalSat in Norway's Arctic regions and TrollSat at the Norwegian Antarctic base on the opposite pole. It is the largest commercial ground station in the world. The first customer was NASA, which uses it for its EOS satellites, NEN and SLR. The European, Japanese and Indian Space Agencies also use it extensively. The business idea for Svalbard satellite station is to provide cost-effect

I almost forgot the most interesting counter-argument to your joke! If the world experiences a major catastrophe where agriculture is severely affected it probably would be quite useful to be able to reach the Svalbard Global Seed Vault [nationalgeographic.com], hehe.

Try finding the seed bank without GPS and keeping an eye out for the very hungry polar bears that roam there!